On the relation between seismicity and magnetic storms

Seismicity variations in a seismically active region of Kazakhstan and Kyrg yzstan are studied before and after magnetic storms with a sudden commencem ent. Aftershocks were eliminated from the 1975-1996 catalog used. It was fo und to be representative of events with an intensity (energy class) of 7 an d more. Two subcatalogs formed from the main catalog included events preced ing (the first subcatalog) and following (the second) magnetic storms. The method of epoch superposition showed that, at a high significance level, th e number of earthquakes occurring after storms increases in some areas (pos itive effect) and decreases in another (negative effect). These effects cou ld not be interpreted in terms of the difference between the energy spectra of earthquakes in respective areas but may be accounted for (at least in p art) by distinctions between their geoelectric sections. The tendency towar d an increase in the number of earthquakes after the storms characterizes t he region as a whole. No correlation between this effect and variations in earth tides has been revealed. Based on estimates of the energy delivered b y magnetic storms and that released by earthquakes, a trigger mechanism und erlying the magnetic storm effect on seismicity is proposed.